County Service Area 11
EPA ID: CA4100582 · 450 people served · 5 ZIP codes
Five years of EPA monitoring have produced no violations for County Service Area 11 — the supplier serving 450 residents has kept every contaminant level within federal limits, a result that places it among the top-performing utilities for systems with a service population of comparable size.
Data: EPA SDWIS Last verified: 2026-04-02
Service Area Map
Coverage area for County Service Area 11 Source: EPA SDWIS service area boundaries.
Service area boundary
Service Area Demographics
The County Service Area 11 serves a community with a median household income of $177,480 and an estimated 109,628 residents across its service area. Approximately 69% of housing stock was built before 1986, which increases the likelihood of lead service lines and older plumbing.
💧 Where Does Your Water Come From?
County Service Area 11's water is pumped from underground aquifers. Groundwater is naturally filtered through rock and soil, but it can be vulnerable to PFAS contamination, nitrates from agriculture, and industrial chemicals that seep into the water table.
About 1% of homes in San Mateo County, California rely on private wells rather than public water systems. Private well owners are responsible for their own water testing and treatment.
Superfund Proximity Note: This service area ranks in the 60th percentile nationally for proximity to Superfund (NPL) sites. Groundwater sources near contaminated sites may face elevated risk from industrial chemicals.
Infrastructure Risk
Comparable Water Systems
Similar-sized systems in California
Estimated Remediation Costs
Average estimated costs across ZIP codes served by this system
Based on national averages for common remediation projects. Actual costs vary by property. Only issues flagged by EPA, FEMA, or state data for each ZIP code are included.
System Overview
County Service Area 11 (EPA ID: CA4100582) is a community water system in California that serves approximately 450 people from groundwater sources.
This system provides water to 5 ZIP codes across 1 community.
Violation History
Lead & Copper
No Lead and Copper Rule sampling data available for this water system.
Need help with your water quality?
Typical cost: Water test: typically $20–$50 (DIY kit) · Professional inspection: $150–$400
Find the Right Water FilterFree tip: Let cold water run for 2 minutes before drinking — this helps flush lead from your pipes.
ZIP Codes Served
- 94061 — Redwood City
- 94062 — Redwood City
- 94063 — Redwood City
- 94064 — Redwood City
- 94065 — Redwood City
Data Sources
This report uses public data from the EPA Safe Drinking Water Information System (SDWIS). View the full compliance record for County Service Area 11 (CA4100582) on EPA.gov.
Frequently Asked Questions
Is County Service Area 11 water safe to drink?
Based on EPA records, County Service Area 11 has no recorded violations in the past 5 years — a positive indicator of water quality management.
How many people does County Service Area 11 serve?
County Service Area 11 serves approximately 450 people across 5 ZIP codes in California.
Where does County Service Area 11 get its water?
The primary water source is groundwater.
Lead Service Line Inventory
Service line breakdown reported under the federal Lead and Copper Rule Improvements (LCRI) inventory requirement:
This system reports zero confirmed lead service lines in its inventory. Unknown-material counts may still warrant verification.
Federal LCRI rule (effective October 2024) requires every public water system to inventory its service lines and complete lead-line replacement within 10 years.
Source: EPA SDWIS Federal Service Line Inventory (Phase 2) · Submitted 2026
ZipCheckup is not affiliated with the utility or state agency. Inventory figures render verbatim from the public LCRI submission cited above; ZipCheckup does not perform inspections or replacements.